Solve 7x ln(5) = 10x ln(7) Confusion

  • Thread starter IntegrateMe
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In summary, the conversation discusses the difference between 5e^(7x) and (5e)^(7x) and how it affects the problem at hand. The correct approach is to treat 5e^(7x) as 5*(e^(7x)) and not (5e)^(7x). This leads to a different equation and a different solution.
  • #1
IntegrateMe
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5e^(7x) = 7e^(10x) ??

7x ln(5e) = 10x ln(7e)

7x * (ln5 + ln e) = 10x * (ln7 + ln e)

7x * (ln5) = 10x * (ln7)

Now I have nowhere to go. What am I doing wrong?
 
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  • #2


5e^(7x) probably means 5*(e^(7x)) not (5e)^(7x) as you are treating it.
 
  • #3


How does that make a difference?
 
  • #4


IntegrateMe said:
How does that make a difference?

All the difference in the world. Try it.
 
  • #5


5*7x ln e = 7 * 10 ln e

35x = 70x?

This doesn't seem right. Can you please explain how I would start this? Is the 5 included in the natural log?
 
  • #6


IntegrateMe said:
5*7x ln e = 7 * 10 ln e

35x = 70x?

This doesn't seem right. Can you please explain how I would start this? Is the 5 included in the natural log?

ln(5*e^(7x))=ln(5)+ln(e^(7x)). It's looking different already, isn't it? Not the same as ln((5e)^(7x))=7x*ln(5e).
 
  • #7


Thank you!
 

FAQ: Solve 7x ln(5) = 10x ln(7) Confusion

How do you solve for x in the equation 7x ln(5) = 10x ln(7)?

To solve this equation, we can use the properties of logarithms to simplify it into a form where we can isolate the variable x. First, we can divide both sides by ln(5) to get 7x = (10/ln(5))x ln(7). Then, we can divide both sides by 7 to get x = (10/ln(5))x ln(7)/7. Finally, we can use the power rule for logarithms to rewrite this as x = (10/7) ln(7)/ln(5).

What is the difference between natural logarithms and common logarithms?

The main difference between natural logarithms (ln) and common logarithms (log) is the base. Natural logarithms use Euler's number, e, as the base while common logarithms use 10 as the base. This means that ln(x) represents the power to which e must be raised to equal x, while log(x) represents the power to which 10 must be raised to equal x.

How can I check if my solution for x in the equation 7x ln(5) = 10x ln(7) is correct?

To check the solution, you can plug the value of x back into the original equation and see if both sides are equal. Another way is to graph both sides of the equation and see if they intersect at the value of x you found. Additionally, you can use a calculator to evaluate both sides of the equation and see if they give the same result.

Can this equation be solved without using logarithms?

Yes, it is possible to solve this equation without using logarithms. One method is to rewrite the equation in exponential form, where 7x is the base and ln(5) is the exponent on one side, and 10x is the base and ln(7) is the exponent on the other side. Then, we can equate the exponents and solve for x. Another method is to use the change of base formula to convert the equation into a form where we can isolate the variable x.

Are there any real-world applications of this type of equation?

Yes, this type of equation often arises in problems involving exponential and logarithmic growth or decay. For example, it can be used to model the growth of a population or the decay of a radioactive substance. It can also be used in finance to calculate compound interest over time. Additionally, it is used in many scientific fields, such as chemistry and biology, to model natural processes that exhibit exponential or logarithmic behavior.

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